1/4" Trim Router Extension Shaft

JR49

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H-M Supporter Gold Member
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Mar 20, 2014
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Can I make, or, I should probably say, is it possible to make, a 4" extension shaft that would have internal threads at one end to screw on the external thread of the trim router shaft (where the collet nut screws on), with the other end machined to accept the 1/4" collet and collet nut, AND, make it concentric enough to spin at the trim routers 25,000 RPM. If the answer is yes, then be prepared, cause my next question is how? Or more precisely, what would be your "order of operations", to insure that the finished part runs true? Happy Thanksgiving, and thanks, JR49
 
Wow JR I am not sure what you intend to do with it, but 4" sounds way to much over hang to me to use as a router. Are you planning on routing with the extension?

David
 
Sounds like that would make one really fast missile/projectile.
Just my thoughts.
 
The tool extensions I have seen for commercial CNC routers are massive, precision ground, and balanced. Normally about 1.5 inch diameter and fit a BT30 spindle. Trying to do this with a trim router sounds like recipe for disaster.:eek:

Maybe you could post what you are trying to accomplish, and we could throw out some ideas.
 
JR 49,
DO NOT do this you will destroy the router and maybe yourself. An extension would need support near the business end.
Have a look at an electric die grinder to see what I mean, these operate in the 25K - 32K band. Bosch, Makita, Fein and others make good ones. At the speeds a router operates at any unsupported imbalance VERY quickly gets out of control.
Add a long nose die grinder to your arsenal you won't regret it. Available in electric or pnumatic.
Air tools are great and a compressor is a necessity.
I've made a 4" extension for a 125mm angle grinder but that also has a heavey duty outer that is secured to the motor casing with a bearing right behind the disk.
Cheers.
 
I was first going to say very bad idea. But, I now remember having a couple of very long nosed ID extensions for my tool post grinder having a similar kind of design and dimensions. However, my tool post grinder does not turn at 25K, more like up to about 12K as I recall? You would REALLY need to make it as concentric and balanced as best you can. And then stand back on your first test, be safe!...Dave.
 
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My gut tells me no, don't do it. I have a couple of 1/4" extensions for my air motors, and they run true, even at full speed. But there is a pucker factor when I have to use them. I never really trust them. I made them, and took extra pains to ensure they were as straight as possible. I even have a set screw holding the (random 1/4" shank) tool in. But what you are suggesting gives pause for a lot of serious thinking. Like what are your end objectives, as has been asked. It's not impossible, but definitely out there on the edge of don't try this at home.
 
I think for a tool post grinder it would be fine, anything else not so much.
 
Tool post grinders can go to pretty high rpms, 42,000 in this example. But its a function SFM, smaller wheel = high rpm, larger wheel = reduced rpm. There are strict do not exceed guidelines.
But the thing I want to mention is the spindle is dedicated to this duty, precision bearings, very low run out, belt drive. Any run out in your router collet or arbor flex or deviation to the extension assembly or weight imbalance means magnified vibration. For grinding I'd be careful. Spinning a shaft is one thing. Grinding with any oscillation is asking for it IMO.
http://www.themacinc-us.com/products.html

Attached pics of their extension arbors. Note ground tapered surfaces that fit a matching socket in spindle.

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Hi JR 49,
I stand by my DO NOT DO what you are thinking of, it is just plain stupid it is that dangerous.
I am uploading a picture of some DIE GRINDERS. These are purpose made for hand use. The air ones are pretty easy to control as the speed can be varied and they don't rotate super fast.
The electric one is nearly 40 years old and has seen much use, (it's on it's second set of brushes). It operates at 27K and you have to be careful and have a very controled touch or there will be a high velocity missile flying off somewhere.
I hope this helps. IF you do build an extension make sure that you build some sort of housing around it and fit a bearing at the business end.
Buy a proper tool and you will live to keep using it.
Reguards
Barry.

HPIM0061.JPG
 
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